9 Grammatical Pitfalls
Old English slæpere "one who sleeps, one who is inclined to sleep much," agent noun from sleep (v.). Meaning "strong horizontal beam" is from c.1600. Meaning "dormant or inoperative thing" is from 1620s. Meaning "railroad sleeping car" is from 1875. Sense of "something whose importance proves to be greater than expected" first attested 1892, originally in American English sports jargon, probably from earlier (1856) gambling slang sense of "unexpected winning card." Meaning "spy, enemy agent, terrorist etc. who remains undercover for a long time before attempting his purpose" first attested 1955, originally in reference to communist agents in the West.
[entry form 1941+, second 1972+, third 1970s+; fr the late 1600s British sleasie, ''thin, flimsy, threadbare,'' of uncertain origin, whence it came to mean ''of inferior workmanship, shoddy''; perhaps fr Sleasie, ''Silesian,'' used of linen cloth from that part of Germany]